Rotating mechanism with arm

ABSTRACT

A device for rotating a work element is disclosed. The device has a support structure, an arm mounted in the support structure in such a way that it can rotate, a rotation drive for rotating the arm around a rotation pin, the rotation drive being located between the arm and the support structure, and a lifting drive. The support structure represents the frame and the arm represents a driven member of a gear. The lifting drive closes the gear between the support structure and the arm. A coupling device is connected in series with the lifting drive in such a way that the lifting drive can be uncoupled from the gear. The coupling device may have a rotating arm and a locking device, for example. The device can be used as a compact rotating device for carrying a blast furnace gun.

FIELD OF THE INVENTION

The invention relates to a swivelling device with jib for swivelling aworking unit between a rest position and an operating position. A deviceof this type is used, for example, to swivel a taphole gun mounted onthe jib into an operating position in front of the taphole of a blastfurnace and for subsequent pressing of the gun against the taphole.

BACKGROUND OF THE INVENTION

A conventional swivelling device for a taphole gun comprises in analready known way a jib, the taphole gun being mounted on its free end.The other end of the jib is pivoted in a fixed supporting structure. Theswivelling range of the jib should be as large as possible to enable thegun to swivel as far as possible from the runner. Furthermore, it shouldbe stated that modern taphole guns operate with increasingly higherplugging pressures. Consequently the swivelling device, which is topress the plugging gun against the taphole, must also be designed forincreasingly higher contact forces.

Hydraulic cylinders are currently used in the taphole plugging machinesto swivel the jib. When work was still carried out with lower pluggingpressures on the blast furnace, rotary motors were also used as the jibdrive instead of the hydraulic cylinders. A taphole plugging machinewith an electric motor is described, for example, in DE-A-895604. Thiselectric motor transmits its force moment via a toothed-wheel and wormmechanism to the jib. A magnetic brake permits locking of the jib in theoperating position. It is obvious that in the case of modern pluggingmachines with extremely high contact pressures such a solution is nolonger economically viable.

A taphole gun with a hydraulic cylinder and hydraulic rotary motor isalready known from U.S. Pat. No. 3,765,663. An arm securely connected tothe jib, on which the piston rod of a double-acting hydraulic cylinderis secured by a first swivel joint, extends radially to the swivellingaxis of the jib. The casing of this hydraulic cylinder is secured by asecond swivel joint to a fixed arm, which projects a long way beyond thesupporting structure of the jib. The hydraulic rotary motor is securedin the jib. It engages via a pinion with a gear wheel securely mountedon the supporting structure of the jib. This rotary motor swivels thejib between a rest and an operating position. The task of the hydrauliccylinder is merely to transmit a force moment to the jib in theoperating position in order to press the gun against the taphole andsubsequently pull it off again. The hydraulic cylinder is switched ononly in a short swivelling range near the furnace. Its two pressurechambers are discharged to the tank over the remaining swivelling range.The stroke of the hydraulic cylinder is designed in such a way thatduring swivelling of the jib the length of the hydraulic cylinder isautomatically adapted to the variable distance between the first andsecond swivel joints. In other words the swivelling device is a closedthree-element mechanism, whereby the supporting structure forms theframe, the supporting arm the driven element, and the hydrauliccylinder, as an element with a variable length, closes the mechanismbetween the supporting structure and the jib.

A swivelling device for a taphole gun, which is intended to becharacterised by its compactness, is already known from U.S. Pat. No.4,247,088. It comprises a jib to carry the taphole gun, a supportingstructure, in which the jib is pivoted at one end about a swivellingaxis, a rotary drive to swivel the jib between its rest position andoperating position and a hydraulic cylinder to generate a contact force.The hydraulic cylinder is supported by a lateral arm of the supportingstructure. It is not securely connected to the jib, but can engage in atooth system when the jib is swivelled into the operating position.

SUMMARY OF THE INVENTION

The present invention is based on the task of creating a more compactswivelling device.

Like the swivelling device from U.S. Pat. No. 4,247,088, a swivellingdevice according to the invention comprises a jib to carry the workingunit; a supporting structure, in which the jib is pivoted at one endabout a swivelling axis; a rotary drive to swivel the jib between itsrest position and its operating position and a stroke generating driveto produce a contact force. In this configuration, as already mentioned,the supporting structure forms the frame, the supporting arm the drivenelement of a mechanism, which is closed by a stroke generating drivebetween the supporting structure and the jib. The swivelling deviceaccording to the invention likewise comprises a coupling device, whichis connected in series to the stroke generating drive in such a way thatthe stroke generating drive can be disconnected from the positivemovement of the mechanism. In other words an automatic change in lengthof the stroke generating drive during swivelling of the jib can beprevented by the coupling device. Consequently the total stroke of thestroke generating drive need be designed only for its actual function,i.e. the generation of a contact force in the operating position. Bydisconnecting the stroke generating drive during swivelling of the jibadditional freedom of design with regard to arrangement of the strokegenerating drive in the swivelling device is obtained. According to theinvention this freedom of design is utilised in that the hydrauliccylinder is arranged along the jib, is supported by the latter and canbear on the supporting structure via the engaged coupling device totransmit a contact force. Consequently the swivelling device accordingto the invention is extremely compact. Furthermore, the powerrequirement of the swivelling device can be clearly reduced in manycases by disconnection of the stroke generating cylinder.

In a first advantageous embodiment the coupling device comprises aswivelling arm, which is pivoted in the supporting structure. The strokegenerating drive is mounted between the swivelling arm and the jib. Withthe coupling device disconnected this swivelling arm can swivel freelyin relation to the supporting structure and the jib, its swivelling axisbeing essentially coaxial with the swivelling axis of the jib. A lockingdevice permits locking of the swivelling arm in the operating positionin relation to the supporting structure, with the result that the strokegenerating drive is engaged in the swivelling mechanism to transmit acontact force.

In a first embodiment a locking device for the swivelling arm describedabove has a bolt which can be inserted into and withdrawn from asuitable oblong hole for locking the swivelling arm in relation to thesupporting structure. The locking bolt can be inserted in and withdrawnfrom the oblong hole e.g. by a short-stroke cylinder.

In a second embodiment a locking device for the swivelling arm describedabove has a swivelling locking bar, which in order to lock theswivelling arm can be swung into a position in which it rests against anabutment when the swivelling arm is in the operating position. Theadvantage of this locking device is that a shock-absorber, which dampensthe coupling of the lifting drive to the swivelling mechanism, can beinstalled relatively easily in the abutment.

Swivelling devices according to the invention are advantageouslysuitable, for example, to carry a taphole gun, the latter being pivotedat the free end of the jib. In a first embodiment of this tapholeplugging machine a rigid control rod is flexibly connected to thetaphole gun and the supporting structure. This control rod thusdetermines the alignment of the taphole gun as a function of theswivelling angle of the jib in an already known way. If the swivellingdevice is equipped with the swivelling arm described above, however, thecontrol rod can also be pivoted on this swivelling arm instead of on thesupporting structure. In this case an active adjusting element, whichallows the length of the control rod to be varied selectively, ismounted in the control rod so that the alignment of the taphole gun canbe determined independently of the jib position.

In an alternative embodiment the coupling device comprises a firstcoupling head at the end of the piston rod of the hydraulic cylinder anda second coupling head on the supporting structure. The two couplingheads are complementary to each other. When the jib is in the operatingposition the first and second coupling heads are arranged in relation toeach other in such a way that the first coupling head can be supportedby the second coupling head by extending the piston rod of the hydrauliccylinder. If the jib is swivelled from its operating position towardsits rest position, the first coupling head is separated from the secondcoupling head and the hydraulic cylinder can now be swivelled freelywith the jib. The jib advantageously has a spring-centered aligningdevice for the hydraulic cylinder pivoted on the jib. This aligningdevice ensures that the hydraulic cylinder always comes to rest in afavorable coupling position when the jib is swivelled into its operatingposition.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Exemplified embodiments of the invention are described in more detail onthe basis of the enclosed drawings.

FIG. 1 shows a plan view of a taphole gun with a swivelling deviceaccording to the invention in the rest position in front of the blastfurnace;

FIG. 2 a plan view of the taphole gun in FIG. 1 in the operatingposition in front of the blast furnace;

FIG. 3 a section along the section line 3—3 in FIG. 1;

FIG. 4 a section along the section line 4—4 in FIG. 3;

FIG. 5 a section as shown in FIG. 3 with an alternative locking device,the latter being shown in the unlocked position;

FIG. 6 the same section as in FIG. 5, the swivelling device being shownin the locked position;

FIG. 7 a plan view as in FIG. 1 with an alternative design of theswivelling device;

FIG. 8 a plan view as in FIG. 2 with the swivelling device according toFIG. 7;

FIG. 9 a section along the broken section line 9—9 in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a taphole plugging machine 10 according to the invention ina rest position in front of a blast furnace 12, which is indicatedschematically by an arc of a circle. This taphole plugging machine 10consists essentially of a swivelling device 14 according to theinvention and an already known taphole gun 16. The latter will not bedescribed in more detail.

The swivelling device 14 comprises a column-type base 18, which forms asupporting structure for a jib 20. Instead of being installed as a baseon the floor, this supporting structure 18 can, of course, also besuspended. The jib 20 is pivoted at one end in this supporting structure18. In FIG. 1 the position of the swivelling axis of jib 20 in thesupporting structure 18 is indicated by the reference number 22. Thisaxis 22 is generally inclined slightly towards the blast furnace inrelation to the vertical. The taphole gun 16 is suspended at the freeend of the jib 20. The position of the swivelling axis of the tapholegun 16 in the jib 20 is shown by the reference number 24.

A relatively short, preferably double-acting hydraulic cylinder 28 liesdirectly along the jib 20. One end of this hydraulic cylinder 28, i.e.the cylinder base in the embodiment shown, is connected by a firstswivel joint 32 to the front end of the jib 20. For this purpose the jib20 advantageously has a lateral projection, on which the first swiveljoint 32 is mounted. The other end of the hydraulic cylinder 28, i.e.the piston rod end in the embodiment shown, is connected via a secondswivel joint 36 to a swivelling arm 38. The latter is pivoted in thesupporting structure 18, so that its swivelling axis is essentiallycoaxial with the swivelling axis of the jib 20.

The mounting of the jib 20 and swivelling arm 38 in the supportingstructure is shown in more detail in FIG. 3. The jib 20 has at itssupported end a cylindrical connection piece 40, which is secured bymeans of a ball bearing 42 to a flange 44 of the supporting structure18. The outer raceway 46 of this ball bearing 42, i.e. the raceway onwhich the connection piece 40 is secured, forms a gear rim 48. A rotarymotor, which may be designed, for example, as a hydraulic motor orelectric motor, is designated 50. This rotary motor 50 is secured to theflange 44 and can engage in the gear rim 48 by means of a pinion 52.Consequently the rotary motor 50 can swivel the pivoted jib 20 about theaxis 22. The exact angular position of the jib 20 is measured by anangle sensor 51 during swivelling. The latter is secured to the flange44 like the rotary motor 50 and can engage in the gear rim 48 by meansof a pinion 53.

The swivelling arm 38 is pivoted at the top end of the column-typesupporting structure 18 by means of a ball bearing 54. As shown in FIG.3, the inner raceway 56 of the ball bearing 54 is secured to a secondflange 58 on the supporting structure 58 and the outer raceway 60 on theswivelling arm 38. The ball bearing 54 is coaxial with the ball bearing42, so that the swivelling axis 22 of the jib 20 is identical with theswivelling axis of the swivelling arm 38.

A locking device is designated 62 in FIG. 3. This locking device 62permits locking of the swivelling arm 38 on the supporting structure 18to prevent rotation. For this purpose it comprises a locking bolt 64,which can be inserted in and withdrawn from an oblong hole 66 in a frontcover plate 68 of the supporting structure 18 (see also FIG. 4). In apreferred embodiment the locking bolt 64 is formed by a piston of ashort-stroke cylinder 70 secured on the swivelling arm 38.

Schematically represented flexible hydraulic connection lines of thehydraulic cylinder 28 are designated 72, 74 in FIG. 3. These hydraulicconnection lines 72, 74 are advantageously incorporated in a hydrauliccircuit 78 via a rotary connection 76. The lower part of the rotaryconnection is secured with prevention of rotation on the supportingstructure 18, whereas the upper part, to which the lines 72, 74 areconnected, is freely rotatable.

To summarise, it should be stated that the swivelling device 14 with thelocked swivelling arm 38 is—from the kinematic point of view—really aclosed three-element swivelling mechanism, whereby the supportingstructure 18 forms the frame, the jib 20 the driven element and thehydraulic cylinder 28 as a sliding element closes the mechanism betweenthe supporting structure and the jib. In this closed three-elementswivelling mechanism the length of the sliding element, i.e. thehydraulic cylinder 28, would have to adapt to the position of the jib20. In other words the stroke of the hydraulic cylinder 28 would have tovary continuously during swivelling of the jib 20 by the rotary motor50. When the swivelling arm 38 is unlocked, however, the hydrauliccylinder 28 is disconnected from the swivelling mechanism, i.e. theswivelling device is—from the kinematic point of view—now an openmechanism with the rotary motor 50 as the sole drive or, in other words,a change in the position of the jib no longer causes a change in thestroke of the hydraulic cylinder 28. The swivelling arm 38 and lockingdevice 62 thus form a coupling device, which is connected in series tothe hydraulic cylinder 28 and with the aid of which the hydrauliccylinder 28 can be disconnected from the swivelling mechanism duringswivelling of the jib 20 by the rotary motor 50.

The method of operation of the swivelling device 14 described above willnow be described in more detail with reference to FIGS. 1 and 2. In FIG.1 the jib 20 with the taphole gun 16 is in a rest position. The pistonrod of the hydraulic cylinder 28 is fully retracted. The locking device62 is unlocked, i.e. the hydraulic cylinder 28 is disconnected from theswivelling mechanism. If the rotary motor 50 is actuated, the jib 20 isswivelled from the rest position in FIG. 1 into the operating positionin FIG. 2. The freely rotatable swivelling arm 38, which is connectedvia the hydraulic cylinder 28 to the jib 20, is swivelled with the jib20 in the direction of the arrow 80. During swivelling of the jib intoits operating position the locking bolt 64 lies above the oblong hole 66in the supporting structure 18 at a specific angular position of the jib20. In this position the short-stroke cylinder 70 can be actuated,whereby the locking bolt 64, which had until now been retracted, entersthe oblong hole 66 of the supporting structure 18 and assumes theposition shown in FIG. 3. The extension of the locking bolt 64 isadvantageously tripped via the angle sensor 51 as a function of theangular position of the jib 20. As soon as the locking bolt 64 isinserted into the oblong hole 66, the piston rod of the hydrauliccylinder 28 can be extended. Consequently the swivelling arm 38 isswivelled in the opposite direction of the arrow 80 until the lockingbolt 64 rests against a first closure 82 of the oblong hole 66 in thesupporting structure 18. When the locking bolt 64 is in this position,the hydraulic cylinder 28 is incorporated in the swivelling mechanismfor transmission of a pressing force to the jib 20. In other words thehydraulic cylinder 28 bears via the swivelling arm 38 and the lockingbolt 64 on the supporting structure 18 in order to exert a force momenton the jib 20, with the result that the taphole gun is pressed againstthe taphole. For subsequent pulling of the gun from the taphole thepiston rod of the hydraulic cylinder 28 is retracted. In this case thelocking bolt 64 first moves in the oblong hole 66 until it rests on asecond closure 84 of the oblong hole 66 in the supporting structure 18.When the locking bolt 64 is in this position, the hydraulic cylinder 28is incorporated in the swivelling mechanism for transmission of a forcemoment acting in the opposite direction to the jib 20. In other words itbears via the swivelling arm 38 and the locking bolt 64 on thesupporting structure 18 in order to swivel the jib 20 away from theblast furnace 12. While the hydraulic cylinder 28 is actuated forpressing on or pulling away the taphole gun 16, the rotary motor 50advantageously idles. During subsequent swivelling of the jib from itsoperating position the locking bolt 64 is withdrawn from the oblong hole66 at a specific angular position of the swivelling arm 38. The rotarymotor 50 can now swivel the jib 20 back into the rest position shown inFIG. 1 without the need for the hydraulic cylinder 28 to change itslength.

The taphole gun 16 is advantageously aligned at the taphole via acontrol rod. A conventional control rod, which is pivoted at one end ona fixed point of the supporting structure 18 and at the other end on thetaphole gun 16 (see, for example, FIGS. 7 and 8), could be used in thiscase. However, a new control rod arrangement is shown in FIGS. 1 and 2.It is a control rod 90 of variable length, which is pivoted at one endon the swivelling arm 38 and at the other end on the taphole gun 16. Thelength of the control rod 90 is varied via a built-in stroke generatingdrive, for example a hydraulic cylinder 92 or a spindle drive. Duringswivelling of the jib 20 from the rest position into the operatingposition the length of the control rod 90 is changed synchronously byadmission of pressure to the hydraulic cylinder 92. The control rod 90rests on the swivelling arm 38 locked by the hydraulic cylinder 28 inorder to swivel the taphole gun 16 about the swivelling axis 24. Thiscontrol rod arrangement has important advantages. Firstly, it should benoted that the control rod 90 is always on the same side of the jib 20.In other words the control rod 96 must not cross the jib 20 duringswivelling. Consequently the overall height of the machine is reduced.Secondly, it should be noted that alignment of the taphole gun duringswivelling can be designed substantially more flexibly than with aconventional control rod. A comparison of FIGS. 1 and 7, for example,reveals that the machine in FIG. 1 has a substantially more compactposition than the machine in FIG. 7. It should also be emphasized thatin this embodiment the jib 20 can perform a complete revolution aboutits swivelling axis 22.

An alternative embodiment of the locking device of the swivelling arm 38will be briefly explained with reference to FIGS. 5 and 6. This lockingdevice comprises a swivelling locking bar 96 on the supporting structure18 and at least one abutment 98 on the swivelling arm 38. In FIG. 5 theswivelling locking bar 96 is shown in the unlocked position of thelocking device. In FIG. 5 the swivelling locking bar 96 is shown restingagainst the abutment 98. A shock-absorber, which dampens the engagementof the hydraulic cylinder 28 in the swivelling mechanism, can beintegrated very easily in the abutment 98. It should be noted that theswivelling device advantageously has two abutments arranged at an angleto each other, the swivelling locking bar resting against the firstabutment when the taphole gun 16 is pressed against the taphole andagainst the second abutment when the taphole gun 16 is pulled away fromthe taphole.

An alternative embodiment of the entire coupling device of the hydrauliccylinder 28 is described with the aid of FIGS. 7 and 8. This couplingdevice comprises a first coupling head 110 at the end of the piston rod130 of the hydraulic cylinder 128 as well as a second coupling head 112on the supporting structure 18. The second coupling head 112, which iscomplementary to the first coupling head 110, is designed as a fixedpoint on the supporting structure 18. When the mounting is in theoperating position (see FIG. 8) the first and second coupling heads 110,122 are arranged in relation to each other in such a way that the firstcoupling head 110 can bear on the second coupling head 112 when thepiston rod 130 of the hydraulic cylinder 128 is extended. In thisposition the hydraulic cylinder 128 is engaged in the swivellingmechanism for transmission of a contact force to the jib 20.

The hydraulic cylinder 128 is pivoted on a projection 132 of the jib 20.A lever 134 connects its swivelling axis to a spring-centered aligningdevice 136 on the jib 20. This aligning device 136 aligns thedisconnected hydraulic cylinder 128 essentially parallel with the jib 20and thus facilitates disconnection of the two coupling heads 110 and 112when the jib 20 is in the operating position.

In FIG. 9 the two coupling heads 110 and 112 are shown in the coupledposition. It can be seen that the first coupling head 110 has twojournals 140′, 140″, which are arranged symmetrically with the axis 144of the hydraulic cylinder 128. In the coupled position these journals140′, 140″ are mounted in corresponding bearing recesses 142′, 142Δ (seeFIG. 7) of the second coupling head 112. The reference number 146indicates a hole in the first coupling head 110, through which a lockingbolt 148 can be inserted. With the aid of this locking bolt 148 thefirst coupling head 110 can be mechanically locked in the supportingstructure, so that the hydraulic cylinder 128 can also be used to pullthe taphole gun 16 from the taphole. The locking bolt 148 can beactuated, for example, by a small hydraulic cylinder 150, which issecured to the supporting structure 18. Alternatively, however, therotary motor 50 can also be designed for pulling the taphole gun 16 fromthe taphole. The force moment required for this purpose is in factsubstantially smaller than the force moment required for pressing thetaphole gun 16 against the taphole.

Finally, it should be noted that the swivelling devices described areparticularly advantageous if a large swivelling angle and a high contactforce are required. Further advantages are their compactness and low oilconsumption. For this purpose it should be noted that a low oilconsumption not only has a favorable effect on the design of thehydraulic system, but in most cases likewise has a positive effect onthe energy consumption of the swivelling device.

What is claimed is:
 1. A device for swivelling a working unit between arest position and an operating position, comprising: a jib to carry theworking unit; a supporting structure, in which the jib is pivoted abouta swivelling axis at one end; a rotary drive between the jib and thesupporting structure for swivelling the jib between its rest positionand its operating position; and a hydraulic cylinder between the jib andthe supporting structure to generate a contact force; the supportingstructure representing a frame and the jib the driven element of amechanism and the hydraulic cylinder closing this mechanism between thesupporting structure and the jib to transmit the contact force to thejib; and a coupling device, which is connected in series to thehydraulic cylinder in such a way that the hydraulic cylinder can bedisconnected from the mechanism; wherein the hydraulic cylinder isarranged along the jib, and is carried by the latter and can bear on thesupporting structure via the engaged coupling device to transmit acontact force; and further comprising a swivelling arm, which is pivotedin the supporting structure in such a way that the swivelling arm ispivoted in relation to the supporting structure and the jib about aswivelling axis, which is essentially coaxial with the swivelling axisof the jib, the hydraulic cylinder being connected to the swivellingarm; and a locking device for locking the swivelling arm in relation tothe supporting structure; wherein the locking device has a bolt, whichcan be inserted in the withdrawn from a corresponding hole to lock theswivelling arm in relation to the supporting structure.
 2. The deviceaccording to claim 1, wherein the locking device has a short-strokecylinder for insertion and withdrawal of the bolt.
 3. The deviceaccording to claim 1, wherein the locking device has a swivellinglocking bar, which in order to lock the swivelling arm can be swivelledinto a position in which it rests against an abutment when theswivelling arm is in the operating position.
 4. The device according toclaim 3, wherein the abutment comprises a shock-absorber.
 5. A tapholeplugging machine comprising a swivelling device according to claim 1;and further comprising: a taphole gun which is pivoted at the free endof the jib; and a control rod which is flexibly connected to the tapholegun and the swivelling arm, the control rod having an actuating drivefor adjustment of its length.
 6. A device for swivelling a working unitbetween a rest position and an operating position, comprising: a jib tocarry the working unit; a supporting structure, in which the jib ispivoted about a swivelling axis at one end; a rotary drive between thejib and the supporting structure for swivelling the jib between its restposition and its operating position; and a hydraulic cylinder betweenthe jib and the supporting structure to generate a contact force; thesupporting structure representing a frame and the jib the driven elementof a mechanism and the hydraulic cylinder closing this mechanism betweenthe supporting structure and the jib to transmit the contact force tothe lib; and a coupling device, which is connected in series to thehydraulic cylinder in such a way that the hydraulic cylinder can bedisconnected from the mechanism; wherein the hydraulic cylinder isarranged along the jib, and is carried by the latter and can bear on thesupporting structure via the engaged coupling device to transmit acontact force; and further comprising: a first coupling head at the endof a piston rod of the hydraulic cylinder; a second coupling head on thesupporting structure complementary with the first coupling head; p2wherein the first and second coupling heads are arranged in relation toeach other in such a way that when the jib is in the operating positionthe first coupling head can bear on the second coupling head bytelescopic extension of the piston rod of the hydraulic cylinder.
 7. Thedevice according to claim 6, further comprising a spring-centeredaligning device for the hydraulic cylinder pivoted on the jib.
 8. Thedevice according to claim 6, further comprising a locking device, whichis assigned to the two coupling heads in such a way that the firstcoupling head can be locked mechanically in the second coupling head. 9.A device for swivelling a working unit between a rest position and anoperating position, said device comprising: a jib having a first end anda second end, said working unit being connect to said first end; asupporting structure in which said second end of said jib is pivotablysupported so as to define a swivelling axis for said jib; a rotary driveconnected between said jib and said supporting structure for swivellingsaid jib about said swivelling axis between said rest position and saidoperating position; a hydraulic cylinder that is arranged laterallyalong said jib; and a coupling device that is capable of: closing aforce transmitting mechanism formed by said supporting structure, saidjib and said hydraulic cylinder when said jib is in said operatingposition, so that a stroke of said hydraulic cylinder in said closedmechanism results in the transmission of a moment of force onto saidjib; and opening said force transmitting mechanism when said jib isswivelled by said rotary drive between said rest position and saidoperating position, so that said hydraulic cylinder is carried by saidjib, remains substantially parallel to said jib and is not subjected tolength variations.
 10. The device according to claim 9, wherein: saidcoupling device includes a swivelling arm that is supported by saidsupporting structure so as to be capable of swivelling relative to saidsupporting structure and to said jib about a swivelling axis that isessentially coaxial with said swivelling axis of said jib, and a lockingdevice for locking said swivelling arm in rotation relative to saidsupport structure; and said cylinder is connected between saidswivelling arm and said jib.
 11. The device according to claim 10,wherein said locking device includes a locking bolt and a short-strokecylinder for actuating said locking bolt and blocking said swivellingarm in said supporting structure.
 12. The device according to claim 11,wherein said short-stroke cylinder is supported by said swivelling armand said locking bolt is capable of engaging an oblong hole in saidsupporting structure, said oblong hole defining two spaced end stops forsaid locking bolt.
 13. The device according to claim 10, wherein saidlocking device includes a swivelling locking bar co-operating and atleast one abutment.
 14. The device according to claim 13, wherein saidabutment comprises a shock-absorber.
 15. The device according to claim9, wherein: said hydraulic cylinder includes a piston rod; said couplingdevice includes a first coupling head supported by said piston rod and asecond, complementary coupling head supported by said supportingstructure; said first and second coupling head being disengaged whensaid jib is swivelled by said rotary drive between said rest positionand said operating position; and said first and second coupling headbeing capable of engaging each other when said jib is in its operatingposition, so that said hydraulic cylinder can bear with its piston rodon said support structure to transmit a moment of force onto said jib.16. The device according to claim 15, wherein: said jib has a lateralprojection; said hydraulic cylinded is pivotably fixed to said lateralprojection; and said device further comprises a spring-centered aligningdevice that is connect between said jib and said hydraulic cylinder soas to align the disconnected hydraulic cylinder essentially parallelwith said jib.
 17. The device according to claim 15, comprising alocking device that is associated with said two coupling heads in such away that said first coupling head can be locked mechanically in saidsecond coupling head.
 18. A taphole plugging machine comprising: ataphole gun; and a swivelling device for swivelling said taphole gunbetween a rest position and an operating position in front of a taphole;said swivelling device including: a jib having a first end and a secondend, said a taphole gun being pivotably connected to said first end ofsaid jib; a supporting structure in which said second end of said jib ispivotably supported so as to define a swivelling axis for said jib; arotary drive connected between said jib and said supporting structurefor swivelling said jib about said swivelling axis between said restposition and said operating position; a hydraulic cylinder that isarranged laterally along said jib; and a coupling device that is capableof: closing a force transmitting mechanism formed by said supportingstructure, said jib and said hydraulic cylinder when said jib is in saidoperating position, so that a stroke of said hydraulic cylinder in saidclosed mechanism results in the transmission of a moment of force ontosaid jib; and opening said force transmitting mechanism when said jib isswivelled by said rotary drive between said rest position and saidoperating position, so that said hydraulic cylinder is carried by saidjib, remains substantially parallel to said jib and is not subjected tolength variations.
 19. The taphole plugging machine as claimed in claim18, wherein: said coupling device includes a swivelling arm that issupported by said supporting structure so as to be capable of swivellingrelative to said supporting structure and to said jib about a swivellingaxis that is essentially coaxial with said swivelling axis of said jib,and a locking device for locking said swivelling arm in rotationrelative to said support structure; and said cylinder is connectedbetween said swivelling arm and said jib.
 20. The taphole pluggingmachine as claimed in claim 19 further comprising: a control rod that isconnected by means of articulations at one end to said taphole gun andat the other end to said swivelling arm; and an active adjusting elementto vary the length of said control rod.
 21. The taphole plugging machineas claimed in claim 18, wherein: said hydraulic cylinder includes apiston rod; said coupling device includes a first coupling headsupported by said piston rod and a second, complementary coupling headsupported by said supporting structure; said first and second couplinghead being disengaged when said jib is swivelled by said rotary drivebetween said rest position and said operating position; and said firstand second coupling head being capable of engaging each other when saidjib is in its operating position, so that said hydraulic cylinder canbear with its piston rod on said support structure to transmit a momentof force onto said jib.
 22. The taphole plugging machine as claimed inclaim 21, wherein: said jib has a lateral projection; said hydrauliccylinder is pivotably supported by said lateral projection; and saiddevice further comprises a spring-centered aligning device that isconnect between said jib and said hydraulic cylinder so as to align thedisconnected hydraulic cylinder essentially parallel with said jib. 23.The taphole plugging machine as claimed in claim 21, comprising alocking device that is associated with said two coupling heads in such away that said first coupling head can be locked mechanically in saidsecond coupling head.